AASHTO T104:99(2020) Standard Method of Test for Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate.
1 .1. This method covers the procedure to he followed in testing aggregates to determine their resistance to disintegration by saturated solutions of sodium sulfate or magnesium sulfate. This is accomplished by repeated immersion in saturated solutions of sodium or magnesium sulfate followed by oven drying to partially or completely dehydrate the salt precipitated in permeable pore spaces. The internal expansive force, derived from the rehydration of the salt upon reimmersion, simulates the expansion of water on freezing. This test method furnishes information helpful in judging the soundness of aggregates subject to weathering action, particularly when adequate information is not available from service records of the material exposed to actual weathering conditions. Attention is called to the fact that test results by the use of the two salts differ considerably and care must be exercised in fixing proper limits in any specifications that may include requirements for these tests.
1 .2. The values stated in SI units are to he regarded as the standard.
Prepare the solution for immersion of test samples from either sodium or magnesium sulfate in accordance with Section 4.1.1 or 4.1.2 (Note 2). The volume of the solution shall he at least five times the solid volume of all samples immersed at any one time.
Note 2—Some aggregates containing carbonates of calcium or magnesium are attacked chemically by fresh sulfate solution, resulting in erroneously high-measured losses. If this condition is encountered or is suspected, repeat the test using a filtered solution that has been used previously to test the same type of carbonate rock, provided that the solution meets the requirements of Sections 4.1.1 and 4.1.2 for specific gravity.
4.1.1. Sodium Sulfate Solution—Prepare a saturated solution of sodium sulfate by dissolving a reagent grade of the salt in water (Note 5) at a temperature of 25°C (77°F) minimum. Add sufficient salt (Note 3) of the anhydrous (Na2SO4) form to ensure not only saturation but also the presence of excess crystals when the solution is ready for use in the tests. Thoroughly stir the mixture during the addition of the salt and stir the solution at frequent intervals until used. To reduce evaporation and prevent contamination, keep the solution covered at all limes when access is not needed. Allow the solution to cool to 20.3 to 21.9°C (68.5 to 71.5°F). Again stir, and allow the solution to remain at the designated temperature for at least 48 h before use. Prior to each use, break up the salt cake, if any, in the container, stir the solution thoroughly, and determine the specific gravity of the solution. When used, the solution shall have a specific gravity not less than 1.154 nor more than 1.171. Discard a discolored solution, or filter it and check for specific gravity.
Note 3—For the solution, 215 g of anhydrous salt per liter of water is sufficient for saturation at 22°C (71 .6°F). However, because this salt is not completely stable and because it is desirable that an excess of crystals be present. the use of not less than 225 g of the anhydrous salt per liter of water is recommended.AASHTO T104 pdf download.